In a conventional art, there is known a stapler which is used for stapling a plurality of papers or the like with a U-shaped staple as office equipments or goods which is widely usefully used.
Prior art has provided a number of staplers having various structures, one of which is shown in FIG. 17 as sectional view (refer to Japanese Patent Laid-open (KOKAI) Publication No. 2002-337065).
Referring to FIG. 17, the stapler includes a horizontal base 1 provided with an anvil 2 for guiding a bending movement of a lower end of a staple, a pivot shaft or pin 3 for a mount portion provided for the horizontal base 1, a staple mount magazine 4 supported by the pivot shaft 3, a pivot shaft or pin 5 for a handle provided for the staple mount magazine 4, a push-down or depressing handle 6 supported by the handle pivot shaft 5. A magazine support spring 7 is disposed between the horizontal base 1 and the staple mount magazine 4, and a handle support spring 8 is also disposed between the staple mount magazine 4 and the push-down handle 6. The staple mount magazine 4 has a structure to which a connected staple assembly cassette 20, into which a number of staples are connected as staple assembly 21, are mounted.
A blade path 9 is formed to one end portion of the staple mount magazine 4, and a staple striking blade plate 10 capable of moving downward in the blade path 9 is connected to the push-down handle 6.
FIG. 18 is a schematic view of a conventional connected staple assembly cassette 20 to be mounted to the staple mount magazine 4. The connected staple assembly cassette 20 has an elongated case 12, in which a connected staple assembly 21 having a number of connected staples is mounted with one end thereof on one longitudinal end side in the case 12, and has a metallic feed spring 13 in the case 12 as a stapler feeding means for urging and sequentially feeding the staples of staple assembly 21 toward the one longitudinal end side or a front end side of the case 12. At a bottom portion of the one longitudinal end side is provided a slit 14 through which the staple is pushed down.
When the connected staple assembly cassette 20 is mounted to the staple mount magazine 4, it is mounted so that the front one staple of the connected staple assembly 21 displaced to one longitudinal end side portion can be easily struck by the staple striking blade plate 10.
Then, when such conventional stapler is used, the connected staple assembly cassette 20 is first mounted to the staple mount magazine 4, and plural sheets of papers are placed on the anvil 2 so as to cover the anvil 2. In this state, the push-down handle 6 is depressed. The push-down handle 6 and the staple mount magazine 4 are lowered together around the pivot shaft 3 against a repulsion force of the magazine support spring 7. At a time when one end side bottom portion of the connected staple assembly cassette 20 reaches above the stacked papers on the anvil 2, the staple mount magazine 4 once stops in its lowering operation. However, the push-down handle 6 is further pushed downward, the push-down handle 6 is pivoted around the handle pivot shaft 5 against the repulsion force of the magazine support spring 7 and a repulsion force of the handle support spring 8. Next, the staple striking blade plate 10 suspending from the push-down handle 6 is lowered along the blade path 9, and then, strikes the front one staple of the connected staple assembly in the staple assembly cassette 20 into the stacked papers.
Most of conventional staplers has substantially the identical structure to that mentioned above, which thus provides a common problem for use.
As mentioned above, the conventional stapler is provided with the horizontal base 1, the pivot shaft 3 for the mount portion, the staple mount magazine 4, the handle pivot shaft 5, the push-down handle 6 and so on. The push-down handle 6 is coupled to the staple mount magazine 4 by way of the handle pivot shaft 5. Moreover, the conventional stapler requires two springs such as magazine support spring 7 and handle support spring 8. The magazine support spring 7 acts to return the depressed staple mount magazine 4 to the original position after the staple mount magazine 4 has been pushed down, and on the other hand, the handle support spring 8 acts to return the depressed push-down handle 6 to the original position after the push-down handle 6 has been pushed down. The magazine support spring 7 and the handle support spring 8 are related independently to the mount portion pivot shaft 3 and the handle pivot shaft 5. The push-down handle 6 is depressed against the repulsion force of the magazine support spring 7 till the staple assembly cassette 20 reaches the stacked papers. After the reaching, the push-down handle 6 is further depressed against the repulsion forces of the handle support spring 8 and the magazine support spring 7. Because of this reason, the staple striking work creates a problem of requiring much more force in the second half striking stage, providing a problem.
The connected staple assembly 21 is pushed by the feed spring 13 in a time when the staple striking blade plate 10 pushes down the front side one staple in the connected staple assembly cassette 20. When the depressing force on the push-down handle is loosened during the staple depressing process and the staple striking blade plate 10 once moves upward, the next staple in the connected staple assembly is pushed by the feed spring 13, and under the state of the front one staple remaining, the next staple is pushed into the slit 14 through which a staple is pushed down, thus both staples being entangled in the slit. In such state, when the handle 6 is further depressed, the staple striking blade plate 10 will depress a plurality of staples at once. As a result, there will cause a trouble in the staple striking process, thus also providing a problem.
Some conventional staplers use no case 12, in which a number of staples are connected by bonding agent and the thus connected staple assembly 21 is directly mounted in the staple mount magazine 4. In such conventional staplers having no case 12, the connected staple assembly 21 will be easily disassembled, and it is difficult for the disassembled staples to be set in the staple mount magazine 4 as they are, and many staples becomes useless. In order to obviate such defect, there is often used the connected staple assembly cassette 20 in which the connected staple assembly 21 is mounted in the case 12.
Usually, the case 12 of the connected staple assembly cassette 20 is disposable. The case 12 is made of synthetic resin, and a metallic feed spring 13 is installed inside the case 12. Accordingly, when the case is disposed of, the feed spring 13 is together disposed of. Such structure is complicated and expensive as a disposable product, and accordingly, the disposal is not reasonable nor economical. This disposable product includes the synthetic resin member and the metal member, so that an environmental load is to also be considered.